Page 42 - Kutnar, Andreja, et al., eds., 2015. Proceedings of the 1st COST Action FP1307 International Conference - Life Cycle Assessment, EPDs, and modified wood. University of Primorska Press, Koper.
P. 42
elopment
of
a
continuous
wood
surface
densification
process
with
a
reduced
environmental
impact
Benedikt
Neyses1,
Dick
Sandberg1,
Olle
Hagman1,
Magnus
Wålinder2
1
Luleå
University
of
Technology,
Wood
Science
and
Engineering,
931
37
SKELLEFTEÅ,
Sweden,
benedikt.neyses@ltu.se;
dick.sandberg@ltu.se,
and
olle.hagman@ltu.se
2
KTH,
Building
Materials,
100
44
STOCKHOLM,
Sweden,
magnus.walinder@byv.kth.se
Keywords:
roller
pressing,
wood
modification,
wood
compression,
thermo
hydro
mechanical
processing
Surface
densification
has
the
potential
to
greatly
increase
the
hardness
of
the
outer
parts
of
wood
materials.
This
increases
the
value
of
low-‐density
species,
such
as
Scots
pine
and
Norway
spruce,
which
are
largely
found
in
boreal
forests.
The
density,
strength,
and
hardness
of
these
species
are
lower
than
those
of
commonly
used
hardwood
species
such
as
oak,
and
the
use
of
these
species
is
rather
limited
in
applications
such
as
flooring
and
table
tops.
Through
densification,
a
significant
improvement
in
the
mechanical
properties
can
be
achieved,
thereby
opening
new
fields
of
application.
The
state
of
the
art
in
the
field
of
surface
densification
is
well
described
by
Navi
&
Sandberg
(2012),
Rautkari
(2012),
and
Laine
(2014).
Recent
studies
in
wood
surface
densification
have
focused
on
processing
parameters
and
their
effect
on
the
properties
of
the
densified
wood.
Laine
et
al.
(2013a)
examined
the
effects
of
compression
temperature
and
press
closing
time
on
the
hardness
of
surface-‐densified
Scots
pine.
Rautkari
et
al.
(2013)
investigated
the
effects
produced
from
varying
degrees
of
densification.
The
thermodynamic
characteristics
of
surface-‐densified
Scots
pine
have
been
studied
by
Kutnar
et
al.
(2012).
An
important
aspect
related
to
densified
wood
is
how
to
eliminate
the
set-‐recovery
after
pressing,
especially
when
the
densified
wood
is
exposed
to
variations
in
moisture.
Rautkari
et
al.
(2010)
observed
complete
set-‐recovery
of
surface-‐densified
spruce
and
beech
without
any
post-‐
treatment
(e.g.
heating)
of
the
densified
wood
material.
Gong
et
al.
(2010)
were
able
to
reduce
the
set-‐recovery
of
densified
wood
by
a
post-‐treatment
involving
steam
injection.
Laine
et
al.
(2013b)
used
a
combination
of
steam
injection
at
200°C
and
drying
with
hot
air.
A
common
feature
of
all
these
processes
is
the
long
treatment
time,
where
the
thermal
treatment
process
exceeded
4
hours
even
with
small
laboratory
specimens.
In
recent
research,
only
limited
focus
has
been
put
on
the
economic
and
environmental
aspects
of
the
densification
process.
Rautkari
(2012)
studied
three
different
surface
densification
approaches,
two
of
them
using
an
ordinary
heated
press
and
one
adapting
a
friction
welding
technique.
All
surface
densification
processes
are
time-‐consuming
batch
processes,
where
a
post-‐
30
of
a
continuous
wood
surface
densification
process
with
a
reduced
environmental
impact
Benedikt
Neyses1,
Dick
Sandberg1,
Olle
Hagman1,
Magnus
Wålinder2
1
Luleå
University
of
Technology,
Wood
Science
and
Engineering,
931
37
SKELLEFTEÅ,
Sweden,
benedikt.neyses@ltu.se;
dick.sandberg@ltu.se,
and
olle.hagman@ltu.se
2
KTH,
Building
Materials,
100
44
STOCKHOLM,
Sweden,
magnus.walinder@byv.kth.se
Keywords:
roller
pressing,
wood
modification,
wood
compression,
thermo
hydro
mechanical
processing
Surface
densification
has
the
potential
to
greatly
increase
the
hardness
of
the
outer
parts
of
wood
materials.
This
increases
the
value
of
low-‐density
species,
such
as
Scots
pine
and
Norway
spruce,
which
are
largely
found
in
boreal
forests.
The
density,
strength,
and
hardness
of
these
species
are
lower
than
those
of
commonly
used
hardwood
species
such
as
oak,
and
the
use
of
these
species
is
rather
limited
in
applications
such
as
flooring
and
table
tops.
Through
densification,
a
significant
improvement
in
the
mechanical
properties
can
be
achieved,
thereby
opening
new
fields
of
application.
The
state
of
the
art
in
the
field
of
surface
densification
is
well
described
by
Navi
&
Sandberg
(2012),
Rautkari
(2012),
and
Laine
(2014).
Recent
studies
in
wood
surface
densification
have
focused
on
processing
parameters
and
their
effect
on
the
properties
of
the
densified
wood.
Laine
et
al.
(2013a)
examined
the
effects
of
compression
temperature
and
press
closing
time
on
the
hardness
of
surface-‐densified
Scots
pine.
Rautkari
et
al.
(2013)
investigated
the
effects
produced
from
varying
degrees
of
densification.
The
thermodynamic
characteristics
of
surface-‐densified
Scots
pine
have
been
studied
by
Kutnar
et
al.
(2012).
An
important
aspect
related
to
densified
wood
is
how
to
eliminate
the
set-‐recovery
after
pressing,
especially
when
the
densified
wood
is
exposed
to
variations
in
moisture.
Rautkari
et
al.
(2010)
observed
complete
set-‐recovery
of
surface-‐densified
spruce
and
beech
without
any
post-‐
treatment
(e.g.
heating)
of
the
densified
wood
material.
Gong
et
al.
(2010)
were
able
to
reduce
the
set-‐recovery
of
densified
wood
by
a
post-‐treatment
involving
steam
injection.
Laine
et
al.
(2013b)
used
a
combination
of
steam
injection
at
200°C
and
drying
with
hot
air.
A
common
feature
of
all
these
processes
is
the
long
treatment
time,
where
the
thermal
treatment
process
exceeded
4
hours
even
with
small
laboratory
specimens.
In
recent
research,
only
limited
focus
has
been
put
on
the
economic
and
environmental
aspects
of
the
densification
process.
Rautkari
(2012)
studied
three
different
surface
densification
approaches,
two
of
them
using
an
ordinary
heated
press
and
one
adapting
a
friction
welding
technique.
All
surface
densification
processes
are
time-‐consuming
batch
processes,
where
a
post-‐
30
